The Pyrenean brook newt (Calotriton asper) is an endemic of cold-water streams and caves, and shows a variaty of phenotypes across its range in the French and Spanish Pyrenees. In collaboration with Olivier Guillaume and Jean Clobert at the CNRS-Moulis, we sampled the species throughout the French side of the Pyrenees and used mtDNA and genome-wide AFLP markers to reveal a striking degree of genetic structure, which indicates that brook newts have extremely restricted dispersal.